Test fixtures are commonly employed to electrically connect electronic circuit devices to be tested to automatic testing equipment operative to determine whether the electronic circuit device conforms to a predetermined standard of quality. Typically, the automatic testing equipment is operative to provide both in-circuit and functional testing. For in-circuit testing, the automatic testing equipment is operative to determine the integrity of the individual components of the electronic circuit device, such as, for example, the intended conductivity of its constituent conductive paths, and the intended resistivity of its constituent resistors. For functional testing, the automatic testing equipment is operative to determine the cooperation of the individual electronic circuit device components to provide the intended device function. It is known to provide separate test fixtures for electrically connecting electronic circuit devices to automatic testing equipment respectively for in-circuit and for functional testing. The utility of this approach is limited, however, due to the time and labor costs incurred in successively connecting the electronic circuit device to the in-circuit fixture and automatic testing equipment, and then to the functional testing fixture and automatic testing equipment; due to the storage space required to maintain an inventory of separate in-circuit and functional testing fixtures; and due to the considerable acquisition costs incurred in procuring separate in-circuit and functional test fixtures, among others. It is also known to provide a test fixture having first and second platens that are movable by first and second vacuum chamber actuators into contact with the electronic circuit device to selectively provide either in-circuit or functional testing as disclosed in U.S. Pat. No. 4,115,735 to Stanford, incorporated herein by reference. Each platen includes a plurality of probes slidably mounted in a corresponding guide that are in electrical communication by individual ones of a plurality of wires to the automatic testing equipment. The utility of this approach is limited, however, due to the increased possibility of leakage and vacuum loss from each of the first and second vacuum chamber actuators; due to the strain on the wires and on the wire/probe termination points occasioned by the movement of the platens; and due to a restriction on the total number of probes that may be employed for a nominal vacuum pressure occasioned by the vacuum leakage at the multiple probe/guide sliding interfaces, among other things.